A probe and a primer capable of collectively detecting microorganisms of the same species while differentiating microorganisms of other species with an object of classification by species of fungus. An oligonucleotide probe for detecting an infectious etiologic microorganism gene includes at least one base sequence selected from the base sequences belonging to one group of the following first to ninth groups. The base sequence groups of first to ninth groups are: first group (SEQ ID NOS:1 to 5); second group (SEQ ID NOS:6 to 10); third group (SEQ ID NOS:11 to 15); fourth group (SEQ ID NOS:16 to 21); fifth group (SEQ ID NOS:22 to 26); sixth group (SEQ ID NOS:27 to 31); seventh group (SEQ ID NOS:32 to 36); eighth group (SEQ ID NOS:37 to 41); and ninth group (SEQ ID NOS:42 to 46).